1. Field of the Invention
The present invention relates to a projection type video display apparatus such as a liquid crystal projector comprising a light source lamp and a light valve for modulating the intensity of light from the light source lamp to display an image.
2. Description of the Background Art
In a projection type video display apparatus utilizing a device such as an LCD (Liquid Crystal Display) and a DLP (Digital Light Processor) as a light valve to display an image, a method of controlling the illuminance (brightness) of a light source lamp depending on the luminance of the image to be displayed to improve a visual contrast feeling has been proposed (see JP-A-03-179886 and JP-A-08-201812).
Conventionally in order to transmit control information for controlling a light source lamp to a lamp control circuit, the control information has been fed to the lamp control circuit by serial UART (Universal Asynchronous Receiver Transmitter) communication, and control information composed of digital data has been transmitted to the lamp control circuit.
In such a method, however, two or more signal lines for information transmission are required, so that the circuit scale of a transmission-side circuit for information transmission is increased, and the scale of a microcomputer required for a receiving-side circuit (lamp control circuit) is also increased.